One of the most heartfelt—and unexpected—remembrances of Aaron Swartz, who committed suicide last month at the age of 26, came from Yale professor Edward Tufte. During a speech at a recent memorial service for Swartz in New York City, Tufte reflected on his secret past as a hacker—50 years ago.

“In 1962, my housemate and I invented the first blue box,” Tufte said to the crowd. “That’s a device that allows for undetectable, unbillable long distance telephone calls. We played around with it and the end of our research came when we completed what we thought was the longest long-distance phone call ever made, which was from Palo Alto to New York … via Hawaii.”

Tufte was never busted for his youthful forays into phone hacking, also known as phone phreaking. He rose to become one of Yale’s most famous professors, a world authority on data visualization and information design. One can’t help but think that Swartz might have followed in the distinguished footsteps of a professor like Tufte, had he lived.

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Swartz faced 13 felony charges and up to 35 years in prison for downloading 4.8 million academic articles from the digital repository JSTOR, using MIT’s network. In the face of the impending trial, Swartz—a brilliant young hacker and activist who was a key force behind many worthy projects, including the RSS 1.0 specification and Creative Commons—killed himself on Jan. 11.

“Aaron’s unique quality was that he was marvelously and vigorously different,” Tufte said, a tear in his eye, as he closed his speech. “There is a scarcity of that. Perhaps we can all be a little more different, too.”

Swartz was too young to be a phone phreak like Tufte. In our present era of Skype and smartphones, the old days of outsmarting Ma Bell with 2600 Hertz sine wave tones and homemade “blue boxes” seems quaint, charmingly retro. But there is a thread that connects these old-school phone hackers to Swartz—common traits that Tufte recognized. It’s not just that, like Swartz, many phone phreaks faced trumped-up charges (wire fraud, in their cases). The best of these proto-computer hackers possessed Swartz’s enterprising spirit, his penchant for questioning authority, and his drive to figure out how a complicated system works from the inside. They were nerds, they were misfits; like Swartz, they were a little more different.

In his new history of phone phreaking, Exploding the Phone, engineer and consultant Phil Lapsley details the story of the 1960s and 1970s culture of hackers who, like Tufte, devised numerous ways to outwit the phone system. The foreword of the book is by Steve Wozniak, co-founder of Apple—and, as it happens, an old-school hacker himself. Before Wozniak and Steve Jobs built Apple in the 1970s, they were phone phreaks. (Wozniak’s hacker name was Berkeley Blue; Jobs’ handle was Oaf Tobar.)

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In 1971, Esquire published an article about phone phreaking called “Secrets of the Little Blue Box,” by Ron Rosenbaum (a Slate columnist). It chronicled a ragtag crew sporting names like Captain Crunch and the Cheshire Cat, who prided themselves on using ingenuity and rudimentary electronics to outsmart the many-tentacled monstrosities of Ma Bell and the FBI. A blind 22-year-old named Joe Engressia was one of the scene’s heroes; according to Rosenbaum, Engressia could whistle at exactly the right frequency to place a free phone call.

A joke ad posted, possibly by the Bell of Pennsylvania security department, at Carnegie Mellon. From Exploding the Phone.

Image courtesy Ken Hopper.

Wozniak, age 20 in ’71, devoured the now-legendary article. “You know how some articles just grab you from the first paragraph?” he wrote in his 2006 memoir, iWoz, quoted in Lapsley’s book. “Well, it was one of those articles. It was the most amazing article I’d ever read!” Wozniak was entranced by the way these hackers seemed so much like himself. “I could tell that the characters being described were really tech people, much like me, people who liked to design things just to see what was possible, and for no other reason, really.” Building a blue box—a device that could generate the same tones that the phone system used to route phone calls, in a certain sequence—required technical smarts, and Wozniak loved nerdy challenges. Plus, the payoff—and the potential for epic pranks—was irresistible. (Wozniak once used a blue box to call the Vatican; impersonating Henry Kissinger he asked to talk to the pope.)

Wozniak immediately called Jobs, who was then a 17-year-old senior in high school. The friends drove to the technical library at Stanford’s Linear Accelerator Center to find a phone manual that listed tone frequencies. That same day, as Lapsley details in the book, Wozniak and Jobs bought analog tone generator kits, but were soon frustrated that the generators weren’t good enough for really high-quality phone phreaking.

Wozniak had a better, geekier idea: They needed to build their own blue boxes, but make them with digital circuits, which were more precise and easier to control than the usual analog ones. Wozniak and Jobs didn’t just build one blue box—they went on to build dozens of them, which they sold for about $170 apiece. In a way, their sophisticated, compact design foreshadowed the Apple products to come. Their digital circuitry incorporated several smart tricks, including a method to make the battery last longer. “I have never designed a circuit I was prouder of,” Wozniak says.

Author Phil Lapsley.

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Like Tufte, Jobs and Wozniak, amazingly, were never busted—though they came close. In one of the most action-packed sequences of the book, Lapsley details a run-in with the law that almost landed the pair in jail in the early 1970s. On a drive from Berkeley to Jobs’ house in Los Altos, Jobs’ car broke down. Wozniak and Jobs walked to a nearby gas station and attempted to use one of their blue boxes to call Captain Crunch—who was by then a friend—for help. The calls didn’t work. Cops turned up and questioned them about the blue box. Wozniak managed to convince an officer that the blue box was a synthesizer, even playing a few tones to demo the device. Incredibly, the cop bought the whole story, letting them go—they even got their blue box back.

Many other phone phreaks were not so lucky. Several of them served prison sentences; many paid exorbitant fines. Phone phreaking still exists today in some quarters, but is, for the most part, an anachronism, supplanted by the rapid growth of computer hacking. But there was still something magical about hacking phones, and the stories are legend to this day. Exults Jobs in a 1998 interview, quoted in Exploding the Phone:“It was the magic of the fact that two teenagers could build this box for $100 worth of parts and control hundreds of billions of dollars of infrastructure in the entire telephone network of the whole world.” You can spot Jobs’ all-consuming ambition, creative vision, and penchant for total control in his happy-go-lucky days of phone phreaking in the ’70s.

Exploding the Phone is Rosenbaum’s Esquire article writ large over 400 densely packed pages. Lapsley lacks Rosenbaum’s flair for language, but he makes up for it with technical depth and an obsessive amount of research. In addition to conducting numerous primary interviews, Lapsley filed over 400 freedom of information requests with the FBI, DOJ, CIA, NSA, FCC, and the National Archives while writing the book. Intriguing details culled from thousands of pages of government records, most notably the FBI files on various phone phreaks, fill the book’s pages.

In the story of the phone phreaks Lapsley sees a greater lesson about the way society ought to handle those who think different. “There is a difference between mere curiosity and true crime, even if we cannot always clearly articulate what the difference is or what we should do about it when we recognize it,” he writes. “At some level, we as a society understand that there is a benefit to having curious people, people who continually push the limits, who try new things. But we’d prefer they not go too far; that makes us uncomfortable.”

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But that discomfort is often a sign that those curious people are on the right track. “If we hadn’t made blue boxes,” Steve Jobs said in 1998, “there would have been no Apple.” After all, as Lapsley points out, most of the phone phreaks didn’t care about making free long-distance calls. It was burning curiosity that motivated them. “There is a societal benefit,” he writes, “to tolerating, perhaps even nurturing … the crazy ones—the misfits, the rebels, the troublemakers, the round pegs in the square holes.” Sometimes those curious misfits turn out to be Steve Jobs, Steve Wozniak, Edward Tufte—or Aaron Swartz.